Title

Author

Defense Date

2010

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Chemistry

First Advisor

Alenka Luzar

Abstract

Understanding hydrophobic effects at different length scales is relevant to many complex and poorly understood everyday phenomena in materials science and biology. In this thesis, a variety of theory/computational methods in statistical physics and statistical mechanics are used to address three separated, but interconnected problems: (1) How solvation free energy scales with a partical size that is charged? This problem has never been attempted to solve before despite its immense importance in colloidal and protein solutions (J. Wang, D. Bratko, K. Leung and A. Luzar, Hydrophobic hydration at different length-scales: manipulating the crossover by charges, to be submitted to J. Stat. Phys. (Special issue on Water and Associated Liquids)); (2) Can onset to capillary evaporation, seen in some protein complexes with large hydrophobic areas be predicted in a simple way? A simple coarse-grained model of water/protein system, which is developed here shows the conditions for wet and dry hydrophobic protein cavities, and is able to reproduce all atom simulation results. The method should serve as an intermediate step between the initial screening of protein hydrophobic cavities and expensive molecular simulations (J. Wang, S. Kudesia, and A. Luzar, Computational probe of dewetting events in protein systems, in preparation for submission to J. Phys. Chem. B); (3) How to predicts hydrophobicity of a mixed surface from the knowledge of its pure constituents? To this end, wetting free energy on synthetic and biological heterogeneous surfaces is studied. Two distinct mechanisms responsible for their non-additivity have been identified in each case (J. Wang, D. Bratko and A. Luzar, Probing surface tension additivity on heterogenous surfaces: a molecular approach, Proc. Natl. Acad. Sci, under revision)